Biological sequencing batch reactor (SBR) and biological sludge stabilisation

Project co-ordinator: Dr. Milenko Roš

At a wastewater treatment plant that is the major source of pollution of the surface and subsurface water we would like to construct a pilot plant sequencing batch reactor of 50-70 l that will be conducted fully automatically. The basic objective of the project is to construct the reactor with all appropriate equipment for regulation and automation that will be capable of conducting all processes automatically (water addition, switch on and switch off of the stirrer, switch on and switching the stirrer on and off, switching aeration on and off, withdrawal of treated water). The SBR process is more stable than a conventional system with activated sludge and at the same time more flexible and controllable.

The first stage of the project is sludge treatment for large wastewater treatment plants (over 10000 PE). The process is a two stage anaerobic-aerobic sludge digestion process, which reduces the organic solids by 50% and completely stabilises and hygienises the sludge. The process is already developed and patented (Slovenia patent No. 21318, Europe: patent application No. PCT/SI03/00035). In the first stage sludge is partially degraded and completely hygienised. Biogas is also produced, which is used to cover the heat and energy needs of the process completely. In the aerobic stage, sludge is then completely degraded, without any offensive odours and pathogens. The only problem encountered was the high ammonia content in backflow (sludge water backflow to the wastewater treatment), which can be solved by maintaining high O2 concentration in the reactor.

The second stage of the project is sludge treatment for small wastewater treatment plants (up to 10000 PE). A completely new aerobic process will be developed. This process will not be self-sufficient in terms of energy (as is tge the one in the first stage above), but it will be more economic than the transportation to a larger treatment plant, where it could be properly treated. The process is composed of several stages in a batch reactor (auto-thermal hygienisation stage, aerobic digestion stage, nitrification/denitrification stage).